The present invention relates to a dopant body of arsenic and a method for the preparation thereof. More particularly, the invention relates to a composite sintered dopant body of arsenic used for doping of a semiconductor such as high-purity silicon, which can be easily prepared and has various advantages in use such as easiness in handling, absence of the problem of dust scattering to cause environmental contamination, long life as a dopant and inexpensiveness and a method for the preparation of such a dopant body of arsenic. The invention also relates to a method for a doping treatment of a semiconductor such as silicon wafers by using the above mentioned dopant body of arsenic.
In the manufacturing process of semiconductor devices, semiconductor substrates such as a high-purity silicon wafer are sometimes doped with arsenic. It is a conventional way that the doping treatment of a silicon wafer with arsenic is conducted by encapsulating the silicon wafer and elementary arsenic in a powdery form in a capsule under vacuum and heating the capsule. A problem in this method is that, when the surface of the arsenic particles is in an oxidized condition, the silicon wafer must be subjected to a heat treatment in vacuum beforehand.
With an object to avoid the troublesomeness of the above mentioned preliminary heat treatment, Japanese Patent Publication No. 53-44789 proposes a method by using silicon arsenide in a crystalline form as the dopant of arsenic. According to the disclosure, a simple pretreatment is sufficient to precede the doping treatment of a silicon wafer which can be conducted to give an accurately controlled amount of arsenic doping without producing any crystalline defects on the surface of the silicon wafer. As a modification of this method using silicon arsenide, Japanese Patent Publications Nos. 57-22209 and 57-22210 propose that the silicon arsenide is shaped into the form of a disc or pellet to facilitate handling in the doping treatment of semiconductor wafers. One of the serious disadvantages in the use of silicon arsenide as an arsenic dopant, which greatly limits the versatility of the method, is due to the fact the silicon arsenide as shaped has a multilayered laminar structure susceptible to cleavage into layers in addition to the low hardness to cause some inconveniences in handling or to decrease the serviceable life of the dopant body with little possibility of repeated use thereof.